Process of preparing a double-sided mosaic electrode



c. c. LARSON Jan. 30, 1951 PROCESS OF PREPARING A DOUBLE-SIDED MOSAICELECTRODE Filed July 1, 1946 FIG. 2

j W w ,7 l I FIG? FIGS

l34-IOII m w S M ML 0 N m T S R H C A T TO R N E Y i atented jan. 30,

PROCESS OF PREPARING A DOUBLE-SIDED MOSAIC ELECTRODE Christian C.Larson, Fort Wayne, Ind., assignor, by mesne assignments, to FarnsworthResearch Corporation, a corporation of Indiana Application July 1, 1946,Serial No. 680,798

Claims. (01. 204-'-24 This invention relates to electrodes fortelevision tubes and particularly to a novel process of preparing adouble-sided mosaic electrode for use in certain types of pictureanalyzing devices.

A double-sided mosaic electrode may be arranged in a picture signalgenerating tube of the charge storage type in such a manner as to havean optical image of the object projected upon one of its surfaces, whileits opposite surface is scanned by an electron beam for developing.picture signals. It is well known in the art that a double-sided mosaicelectrode will appreciably improve the performance of picture signalgenerating tubes of the charge storage type. It is feasible, forexample, to provide an accelerating electrode opposite thephotosensitive surface of the mosaicfor collecting the photoelectronswhich are liberated from the mosaic by the action of the light. Thiswill increase the signal output of the tube by saturating thephotoemission and improve the signal-to-noise ratio. Furthermore, thescanning beam which may be arranged to the rear of the mosaic electrodemay have a common axis with the optical system provided for imaging theobject on the mosaic electrode. Thus, the so-called keystone effect iseliminated which is caused ina conventional picture analyzing tube ofthe cathode ray type by the necessity to arrange the scanning beam at anacute angle with respect to the mosaic electrode. An appreciableimprovement of the signal-to-noise ratio of the image orthicon may alsobe expected by utilizing a double-sided mosaic electrode therein.

Numerous attempts have been made to provide a double-sided mosaicelectrode which essentially consists of an insulating sheet or foilhaving a multitude of metallic plugs extending .therethrough andinsulated from each other. Thus, it has been suggested to provide a wirescreenwith an insulating layer and to fill the interstices of theinsulated screen with a paste of a metal oxide suspended in abinderwhich isthereafter heated to reduce the oxide and evaporate the binderof the paste. However, since the thickness of the wire screen is of theorder of .001 inch, it is obviously extremely difficult to fill the verysmall interstices in the wire screen uniformly with a metallic paste. Ithas also been suggested to electroplate a metal onto a'continuousconductor provided on one of the surfaces of the insulated wire screen,

thereby to fill the interstices of thescreen with metallic plugs.However, the difficulties of removing this conductor again, such as bygrinding, are appreciable. Furthermore, the thus applied metal willnormally not adhere to the walls of the interstices of the insulatedwire screen so that the metallicplugs are liable to fall out.

t is the principal object of the present invention, therefore, toprovide a novel processof preparing a double-sided mosaic electrodesuitable foruse in cathode ray television trans mitting tubes.

. A further object of the invention is to provide a simple andconvenient method of preparing a double-sided mosaic electrodeadaptedfor use in a picture analyzing device for the transmission of televisionpictures of high definition.

In accordance with the present invention, the

process of preparing a double-sided mosaic electrode from a fine meshmetallic screen comprises the steps of coating the screen with an'ielectrically insulating substance, and then coating one face of thescreen and the inner walls of the interstices thereof with anelectrically conducting material. The face of the screen coated with theconducting material is now covered with a removable insulating layer,and the interstices of the screen are filled with a metal byelectroplating it onto the conductingmaterial,

that is, onto the conducting material on the in the appended claims.

In the accompanying drawing: 7 Fig. 1 is a plan view on greatly enlargedscale of a fragmentary portion of a very fine mesh metallic screenutilized as a base of a double sided mosaic electrode in accordance withthe invention;

Fig. 2 is a sectional view taken on line '2-2 of Fig. 1 of the fine meshmetallic screen;

Figs. 3 to 9 are sectional views similar to Fig.

2 illustrating consecutive steps in the process of preparing adouble-sided mosaic electrode in accordance with the present invention;v

Fig. 3 illustrates the screen coated with a reinforcing metallic layer;

Fig. 4 illustrates the screen of Fig. 3 provided with an insulatingsubstance;

Fig. 5 illustrates the screen of Fig. 4 covered on one of its faces andon the inner walls of its interstices with a conducting. material;

Fig. 6 illustrates the screen of Fig. 5 covered on its metal coatedsurface with an insulating layer applied thereto by a glass plate;

Fig. '7 illustrates the screen of Fig. 6 provided with metallic plugsin" the interstices of the screen;

Fig. 8 illustrates the screen of Fig. '7 with the insulating layerremoved; and

Fig. 9 illustrates the screen of Fig. 8 with the conducting materialremoved from the face of the screen, the screen being now ready for use.

Referring to the drawing, there is shown in Figs. 1 and 2 a very finemesh metallic screen I which may, for example, consist of copper.Metallic screen I is provided with a multiplicity of apertures orinterstices 2 which preferably are of circular shape as illustrated inFig. 1. Metallic screen I may be an 800 or 1,000 mesh screen, that is,there are 800 or 1,000 holes per linear inch, respectively,corresponding to 640,000 holes or. 1,000,000 holes persquare inch. Thus,the number of interstices 2 is so large that at.v least three and.preferably. four interstices or holes are covered. by any pictureelement. in a conventional. picture analyzingv tube of the cathode raytype. Screen I. may have a thickness of .0001 inch. Alternatively,screen I may consist of a very fine mesh Wire screen instead of a veryfine mesh perforated metallic sheet or foil.

Metallic screen I may now be coveredas shown in Fig. 3 with areinforcing metallic layer 3 which may be applied, for example, byevaporation. Metallic layer 3 covers both faces of, screen I as well'asthe inner walls ofinterstices 2. Metallic layer. 3 may, for example,consist of gold for a purposeto be explained hereinafter. However, it isto be understood thatit is not necessary tocoat screen I with a metalliclayer such as 3.

Metallic screen I Which may or may not be covered withmetallic layer 3is now coated with an electrically insulating substance indicated at 4in Fig. 4 which covers the entire surface of screen I including theinner-walls of interstices 2. Insulating substance 4 may, consist, forexample, of calcium fluoride or silicium oxide. Thus, insulatingsubstance 4 maybe applied, for example, by evaporating quartz ontometallic screen I in such a manner that; the entire surface thereof iscovered with a quartz layer. Screen I is now electrically insulated,

The thus insulated metallic screen I is then coated with an electricallyconducting material.

5, such as copper which may be dissolved with. an acid, or with aluminumwhich may be dissolved with an alkaline hydroxideincludingsodiumhydroxide and potassium hydroxide. Conducting material 5 is applied,such as by evaporation, to face li Of screen I and to the inner wallsofinterstices 2 as shown in Fig.5. Accordingly, the opposite face of.metallic screen. Iis free from conducting material 5 so that insulating,sub.- stance 4 is uncovered.

Face '6 of metallic screen Iwhich has previously been coated withelectrically conducting material 5 is now covered with a removableinsulating layer indicated at I in Fig. 6. Removable insulating layer Imay, for example, consist of a lacquer which may be pressed against face6 of screen I by glass plate 8- Thus, conducting material 5 on face 6 ofscreen I is entirely covered by insulatinglayer 'I- while the conductingmaterial 5 is still exposed .in the inner walls of interstices 2.

Conducting,,ma terial 5. on the inner walls of.

interstices 2 which may consist of copper or aluminum as pointed outhereinbefore, may be used in accordance with the present invention as anelectrode for filling interstices 2 with a metal III which iselectroplated onto conducting material 5. Conducting material 5 on face6 of screen I is covered by insulating layer I so that metal I0 cannotbe deposited thereon. As shown in Fig. '7, interstices 2 are filled bymetallic plugs II] which may, for example, consist of gold or platinum,that is, of any metal which is resistant against acids or bases.Electrical contact may be made to conducting material 5 on the innerwalls of interstices 2 from face 6 of screen I. Metallic plugs I0 willstrongly adhere to conducting material 5 on the inner walls ofinterstices 2.

The exposed faces of metallic plugs I0 may be provided at this stagewith caps I I by electroplating a metal, such as silver thereon, whichmay be made photosensitive in accordance with conventional practice.Electrical contact for the electrodeposition of caps II may be madeagain through metallic plugs IIlto conducting material 5 onfaceGofscreen I.

Insulating layer I and glass plate 8. are. now removed by dissolvinglayer I, in a. suitable solvent, andthe resulting screen, is illustratedin Fig. 8. Accordingly, conducting material 5 on face 6 of screenI isexposed again.

The last step of the process of the invention consists in removingconducting material. 5 from face 6 of screen I. If conducting material 5consists, forexample, of copper, it may be re-. moved by a suitable acidsuch as nitric acid, sulphuric acid or. hydrochloric acid, which willnot dissolve metallic plugs I0 which may consist of gold or platinum.Caps II may consist of a.

silver layer of such a thickness that the silver will not be dissolvedbefore copper layer 5 on face 6 of screen I has been entirely dissolved.Alternatively, conducting material 5 may consist of aluminum. In thatcase aluminum layer 5 exposed on face 6 of screen I, may be dissolved bysodium hydroxide or potassium hydroxide. Metallic plugs I0 shouldconsistof a material such as gold or platinum which is resistant to thealka. line hydroxide used for dissolving aluminum layer 5.

It is to be, understood that caps II need not beprovided incasemetallic-plugs I0 consist of gold because gold may also be madephotosensitive.

The-finished screen is-illustrated in Fig. 9 and consists of .arnultiplicity of; metallic plugs It insulated from each other byinsulating substance 4. One of the facesof metallic plugs I0 may be madephotosensitive in order to develop an electricalcharge image when lightimage is projected thereon. The, reverse face of screen I, which may beface 6, maythen be scannedby an electron beam for developing picturesignals.

Reinforcing metallic layer '3' which may consistof gold further servesthe purpose of protecting screen l--wh-ich may consist of a base metal,such as copper, frornthe. action of the acid .or the alkaline hydroxide.utilized for removing the exposed portion of conductingmaterial 5.the-acid or base maydissolve, metallic screen I through pin. holesorcracks-in'insulating substance 4 which normally would protect metallicscreen I from the action of the. acid or base. Sincethethiclmessofmetallic screen I is of the order of .0001inch, abasemetal-such ascopper willbe dissolvedlalmost instantly by anacid if it isnot'pr'ote'cted over its entire surface-by insulat-.

ing substance 4..

Thus,

While there has been described what is at present considered thepreferred embodiment of the invention, it will be obviousto thoseskilled in-the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes andmodificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. The process of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with an elec--trically insulating substance, coating one face of "said screen and theinner walls of the interstices thereof with an electrically conductingmaterial, covering the face of said screen coated with said conductingmaterial with a removable insulating layer, filling said intersticeswith a metal by electroplating it onto said conducting material, andremoving said insulating layer and said conducting material from theface of said screen coated therewith.

2. The process of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with anelectrically insulating substance, coating one face of said screen andthe inner walls of the interstices thereof withan electricallyconducting material, covering the surface of said screen coated withsaid conducting material with a removable insulating layer, filling saidinterstices with a metal by electroplating it onto said conductingmaterial, electroplating onto one of the exposed surfaces of said metalin said interstices a substance which may be photosensitized, andremoving said insulating layer and said conducting material from theface of said screen coated therewith.

3. The method of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with a metalliclayer, coating said metallic layer with an electrically insulatingsubstance, thereafter coating one face of said screen and the innerwalls of the interstices thereof with an electrically conductingmaterial, covering the face of said screen coated with said conductingmaterial with a removable insulator, filling said interstices with ametal by electroplating it onto said conducting material on'said innerwalls, and removing said insulator and said conducting material from theface of said screen coated therewith.

4. The method of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with a metalliclayer, coating said metallic layer with an electrically insulatingsubstance, thereafter coating one face of said screen and the innerwalls of the interstices thereof with an electrically conductingmaterial, covering the face of said screen coated with said conductingmaterial with a removable insulator, filling said interstices with ametal by electroplating it onto said conducting material on said innerwalls, electroplating onto one of the exposed surfaces of said metal insaid interstices a'substance which may be photosensitized, and removingsaid insulator and said conducting material from the face of-said screencoated therewith.

5. The method of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with anelectrically insulating substance, thereafter coating one face of saidscreen and the inner Walls of the interstices thereof with a first metalwhich may be dissolved by a predetermined sol-' vent, covering the faceof said screen coated with said first metal with a removable insulatinglayer, filling said interstices with a second metal which issubstantially not dissolved by said solvent by electroplating it ontosaid first metal on said inner walls, removing said insulating layer,and removin said first metal from the face of said screen coatedtherewith by dissolving it with said solvent.

6. The method of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with a materialwhich is resistant to a predetermined solvent, coating said materialwith an electrically insulating substance, thereafter coating one faceof said screen and the inner walls of the interstices thereof withafirst metal which may be dissolved by said solvent, covering the faceof said screen coatedwith said first metal with a removable insulatinglayer, filling said interstices with a second metal which issubstantially not dissolved by said solvent by electroplating it ontosaid first metal on said inner walls, removing said insulating layer,and removing said first metal from the face of said screen coatedtherewith by dissolving it with said solvent.

7. The method of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with a materialwhich is resistant to a predetermined solvent, coating said materialwith an electrically insulating substance, thereafter coating one faceof said screen and the inner walls of the interstices thereof with afirst metal which may be dissolved by said solvent, covering the face ofsaid screen coated with said first metal with a removable insulatinglayer, filling said interstices with a second metal which issubstantially not dissolved by said solvent by electroplating it ontosaid first metal on said inner walls, electroplating onto one of theexposed surfaces of said second metal in said interstices a substancewhich may be photosensitized, removing said insulating layer, andremoving said first metal from the face of said screen coated therewithby dissolving it with said solvent.

8. The process of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with anelectrically insulating substance, thereafter coating one face of saidscreen and the inner walls of the interstices thereof with a first metalwhich may be dissolved by a predetermined acid, covering the face ofsaid screen coated with said metal with a removable insulating layer,filling said interstices with a second metal which is not dissolved bysaid acid by electroplating it onto said first metal on said innerwalls, removing said insulating layer, and removing said first metalfrom the face of said screen coated therewith by dissolving it withsaid-acid.

9. The process of preparing a double-sided mosaic electrode from a finemesh metallic screen which comprises coating said screen with a firstmetal resistant to a predetermined acid, coating said metal with anelectrically insulating substance, thereafter coating one face of saidscreen and the inner walls of the interstices thereof with a secondmetal which may be dissolved by said acid, covering the face of saidscreen coated with said second metal with a removable insulating layer,filling said interstices With a metal which is not dissolved by saidacid by electroplating it onto said second metal on said inner smearswalls, i'emoving'said insulating l'ayer,rand:removing saidsecondmetalifrom the face-of said screen coated -therewith -by dissolving itwith said :acid. 10. "The 'process of preparing a idouble-sided mosaicelectrodefrom a fine mesh metallic screen which comprises coating saidscreen with an electrically insulating substance, thereafter-coating oneface-of said screen and the'inner walls: of theinterstices thereof withcopp'er,-covering the face of said screen coatedwith said copper with arem'ovable insulating'1ayer,'filling said interstices wvith gold byelectroplating it onto said copper on said inner walls,- removing saidinsulating' -layer, and removing said copper 'from the :face of saidscreen coated therewith by-dissolving it' with an-acid.

11. The processof preparing a double-sided 1 mosaic electrodefrom a finemesh metallic screen which comprises coating said screen with-gold,coatingsaid gold with an electrically insulating sub'stance, thereaftercoating one face of said s'creen -and the inner walls of the intersticesthereof With copper, coveringlthe face of said screen coated with saidcopper with a remova- "ble insulating layer,'filling said intersticeswith gold by electroplating it onto said copper on said inner walls,removing said insulatinglayer, and removing said copper from the face ofsaid screen :co'ated-therewithby dissolving it with an acid. 12. Themethod of preparinga.double-sided mosaic electrode from a fine meshmetallic screen which comprises coating said screen with an electricallyinsulating substance, thereafter coat- "in'g ione face: of said screenand the inner walls er the interstices thereof with a base metal which-may" be "dissolved by a predetermined alkaline hydroxide, covering-theface of said screen coat 'ed'withsaid' base metal with a removableinsulating layer, filling said interstices with a noble metal which isnot dissolved by said alkaline hy- 1droxideby electroplating it ontosaid base metal .on' saidinner walls, removing said insulating layer,ancl removing said base metal from the :faceJof: said screen coatedtherewith by dissolv- -.ing itwith said alkaline hydroxide.

13. LThemethod of preparing a double-sided mosaic electrode from a finemesh metallicscreen which comprises coating said screen with a metal-110i layer resistant to a predetermined alkaline :hydroxide, coatingsaid metallic. layer with an electrically insulating substance,thereafter coat- :ing one face of said screen and the innerwalls o1 the.interstices thereof with a base -metal which maybe 'dissolvedby saidalkaline hydroxide, cov- -ering the face of said screen coated with saidbase metal rwith a removable insulating layer, r-filling' saidinterstices with a noble metal which 8 is :not dissolved bysaidvalkaline :hydroxide by electroplating'it ontosaid-base metalonsaid-:in-

ner awalls, :removing said insulating layer, and -removing said'basemetal from the face of said screen coated .therewith by dissolving .-itwith said alkaline hydroxide.

:14. The .method .of preparing a doublesided mosaic electrode from afine meshiinetallic screen which comprises coating said screen with anelec- 11 trically insulating substance thereafter coating one face ofsaid-screen and the inner walls of {the interstices thereof withaluminum,.cover ing the face i of said gscreen coated with said alumihumwith a removable insulating layer filling said 15 interstices with goldby electroplating it onto .-,said aluminum on Said inner walls, removing;said insulating layer and removing said aluminumfrom the face of.-saidj screen coated there- .-with byrdissolving it with an alkalinehydroxide, 15. The method of preparing a double-sided ,-mosaicelectrodefrom a fine mesh metallic screen vWhichcomprises. coating saidscreenwitha gold layer, coating said gold layer with an electricallyinsulatingsubstance; thereafter coating one face of said screen and theinner walls of'the interstices thereof .with aluminum, covering the faceof said screen coated with saidaluminum .with a removable insulatinglayer, filling said interstices -.with gold byelectroplating it ontosaid aluminum qon said innerswalls, removing said insulating layer,. andremoving saidaluminum from the face of said screen coated therewith bydissolving itwith :an alkaline hydroxide.

CHRISTIAN C. LARSON.

.REFEBENCES orrsn .'The following references are-of record in; the fileof this patent:

UNITED STATES PATENTS :Number Name Date 577,070 ;Sandham Feb. 16, 1897.-997-,6-10 -Feldkamp July 11, 1911 1,243,654 Clark Oct. 16, 1917 A1,323,167 1Denny Nov. 25, 1919 ,1,7 92,197 Stresau, Feb. 10,19312,045,984 Flory June 30, 1936 2,047,369 Hickok July 14, 19.36 2,182,578Blumlein et a1 Dec. 5, 1939 2,217,334 Diggory Oct.;8, 1940 2,226,384Vorris Dec. 24, 19.40

.FOREIGN PATENTS Number Country Date 335,161 Great Britain Apr. 14, 193052 4,354 Great, Britain Aug. 5, 1940

1. THE PROCESS OF PREPARING A DOUBLE-SIDED MOSAIC ELECTRODE FROM A FINEMESH METALLIC SCREEN WHICH COMPRISES COATING SAID SCREEN WITH ANELECTRICALLY INSULATING SUBSTANCE, COATING ONE FACE OF SAID SCREEN ANDTHE INNER WALLS OF THE INTERSTICES THEREOF WITH AN ELECTRICALLYCONDUCTING MATERIAL, COVERING THE FACE OF SAID SCREEN COATED WITH SAIDCONDUCTING MATERIAL WITH A REMOVABLE INSULATING LAYER, FILLING SAIDINTERSTICES WITH A METAL BY ELECTROPLATING IT ONTO SAID CONDUCTINGMATERIAL, AND REMOVING SAID INSULATING LAYER AND SAID CONDUCTINGMATERIAL FROM THE FACE OF SAID SCREEN COATED THEREWITH.